The present invention relates to drive mechanisms, and in particular to a drive unit for adjustable, hospital-type beds.
Adjustable beds, such as those described in U.S. Pat. Nos. 3,919,727; 3,414,913; 3,281,872; and 3,281,873, which are hereby incorporated by reference herein, are used in hospitals, nursing homes, and other similar institutions, particularly for the care of non-ambulatory patients. Such adjustable beds usually have three basic movements of functions, including a pivoting head section, a pivoting leg section, and a vertically adjustable mattress support to vary the elevation of the patient to a selected height. The bed sections are adjustable to provide patient comfort, as well as a wide range of therapeutic positions. In some beds, an adjustable center section and/or tilt provides a fourth function to achieve an even wider range of bed configurations.
Heretofore, each adjustable bed section or function was typically powered by a separate gearmotor. Since gearmotors are relatively expensive, and have comparatively little actual running time during the effective life of the bed, such designs are quite expensive, and economically inefficient.